[PATCH 6.4 201/800] igc: Retrieve TX timestamp during interrupt handling

Greg Kroah-Hartman
2023-07-16T20:02:14Z

From: Vinicius Costa Gomes <vinicius.gomes@intel.com>

[ Upstream commit afa141583d82725f682b2fa762cb36a07f58b3f3 ]

When the interrupt is handled, the TXTT_0 bit in the TSYNCTXCTL
register should already be set and the timestamp value already loaded
in the appropriate register.

This simplifies the handling, and reduces the latency for retrieving
the TX timestamp, which increase the amount of TX timestamps that can
be handled in a given time period.

As the "work" function doesn't run in a workqueue anymore, rename it
to something more sensible, a event handler.

Using ntpperf[1] we can see the following performance improvements:

Before:

$ sudo ./ntpperf -i enp3s0 -m 10:22:22:22:22:21 -d 192.168.1.3 -s 172.18.0.0/16 -I -H -o -37
| responses | TX timestamp offset (ns)
rate clients | lost invalid basic xleave | min mean max stddev
1000 100 0.00% 0.00% 0.00% 100.00% -56 +9 +52 19
1500 150 0.00% 0.00% 0.00% 100.00% -40 +30 +75 22
2250 225 0.00% 0.00% 0.00% 100.00% -11 +29 +72 15
3375 337 0.00% 0.00% 0.00% 100.00% -18 +40 +88 22
5062 506 0.00% 0.00% 0.00% 100.00% -19 +23 +77 15
7593 759 0.00% 0.00% 0.00% 100.00% +7 +47 +5168 43
11389 1138 0.00% 0.00% 0.00% 100.00% -11 +41 +5240 39
17083 1708 0.00% 0.00% 0.00% 100.00% +19 +60 +5288 50
25624 2562 0.00% 0.00% 0.00% 100.00% +1 +56 +5368 58
38436 3843 0.00% 0.00% 0.00% 100.00% -84 +12 +8847 66
57654 5765 0.00% 0.00% 100.00% 0.00%
86481 8648 0.00% 0.00% 100.00% 0.00%
129721 12972 0.00% 0.00% 100.00% 0.00%
194581 16384 0.00% 0.00% 100.00% 0.00%
291871 16384 27.35% 0.00% 72.65% 0.00%
437806 16384 50.05% 0.00% 49.95% 0.00%

After:

$ sudo ./ntpperf -i enp3s0 -m 10:22:22:22:22:21 -d 192.168.1.3 -s 172.18.0.0/16 -I -H -o -37
| responses | TX timestamp offset (ns)
rate clients | lost invalid basic xleave | min mean max stddev
1000 100 0.00% 0.00% 0.00% 100.00% -44 +0 +61 19
1500 150 0.00% 0.00% 0.00% 100.00% -6 +39 +81 16
2250 225 0.00% 0.00% 0.00% 100.00% -22 +25 +69 15
3375 337 0.00% 0.00% 0.00% 100.00% -28 +15 +56 14
5062 506 0.00% 0.00% 0.00% 100.00% +7 +78 +143 27
7593 759 0.00% 0.00% 0.00% 100.00% -54 +24 +144 47
11389 1138 0.00% 0.00% 0.00% 100.00% -90 -33 +28 21
17083 1708 0.00% 0.00% 0.00% 100.00% -50 -2 +35 14
25624 2562 0.00% 0.00% 0.00% 100.00% -62 +7 +66 23
38436 3843 0.00% 0.00% 0.00% 100.00% -33 +30 +5395 36
57654 5765 0.00% 0.00% 100.00% 0.00%
86481 8648 0.00% 0.00% 100.00% 0.00%
129721 12972 0.00% 0.00% 100.00% 0.00%
194581 16384 19.50% 0.00% 80.50% 0.00%
291871 16384 35.81% 0.00% 64.19% 0.00%
437806 16384 55.40% 0.00% 44.60% 0.00%

[1] https://github.com/mlichvar/ntpperf

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Stable-dep-of: c789ad7cbebc ("igc: Work around HW bug causing missing timestamps")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/intel/igc/igc.h | 2 +-
drivers/net/ethernet/intel/igc/igc_main.c | 2 +-
drivers/net/ethernet/intel/igc/igc_ptp.c | 15 +++++----------
3 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
index 70de8b9bbe591..9dc9b982a7ea6 100644
--- a/drivers/net/ethernet/intel/igc/igc.h
+++ b/drivers/net/ethernet/intel/igc/igc.h
@@ -229,7 +229,6 @@ struct igc_adapter {

struct ptp_clock *ptp_clock;
struct ptp_clock_info ptp_caps;
- struct work_struct ptp_tx_work;
/* Access to ptp_tx_skb and ptp_tx_start are protected by the
* ptp_tx_lock.
*/
@@ -666,6 +665,7 @@ int igc_ptp_set_ts_config(struct net_device *netdev, struct ifreq *ifr);
int igc_ptp_get_ts_config(struct net_device *netdev, struct ifreq *ifr);
void igc_ptp_tx_hang(struct igc_adapter *adapter);
void igc_ptp_read(struct igc_adapter *adapter, struct timespec64 *ts);
+void igc_ptp_tx_tstamp_event(struct igc_adapter *adapter);

#define igc_rx_pg_size(_ring) (PAGE_SIZE << igc_rx_pg_order(_ring))

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index d0c067da7aac8..5f2e8bcd75973 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -5245,7 +5245,7 @@ static void igc_tsync_interrupt(struct igc_adapter *adapter)

if (tsicr & IGC_TSICR_TXTS) {
/* retrieve hardware timestamp */
- schedule_work(&adapter->ptp_tx_work);
+ igc_ptp_tx_tstamp_event(adapter);
ack |= IGC_TSICR_TXTS;
}

diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c b/drivers/net/ethernet/intel/igc/igc_ptp.c
index 42f622ceb64bb..cf963a12a92fe 100644
--- a/drivers/net/ethernet/intel/igc/igc_ptp.c
+++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
@@ -540,8 +540,6 @@ static void igc_ptp_clear_tx_tstamp(struct igc_adapter *adapter)
{
unsigned long flags;

- cancel_work_sync(&adapter->ptp_tx_work);
-
spin_lock_irqsave(&adapter->ptp_tx_lock, flags);

dev_kfree_skb_any(adapter->ptp_tx_skb);
@@ -724,16 +722,14 @@ static void igc_ptp_tx_hwtstamp(struct igc_adapter *adapter)
}

/**
- * igc_ptp_tx_work
- * @work: pointer to work struct
+ * igc_ptp_tx_tstamp_event
+ * @adapter: board private structure
*
- * This work function checks the TSYNCTXCTL valid bit to determine when
- * a timestamp has been taken for the current stored skb.
+ * Called when a TX timestamp interrupt happens to retrieve the
+ * timestamp and send it up to the socket.
*/
-static void igc_ptp_tx_work(struct work_struct *work)
+void igc_ptp_tx_tstamp_event(struct igc_adapter *adapter)
{
- struct igc_adapter *adapter = container_of(work, struct igc_adapter,
- ptp_tx_work);
struct igc_hw *hw = &adapter->hw;
unsigned long flags;
u32 tsynctxctl;
@@ -1004,7 +1000,6 @@ void igc_ptp_init(struct igc_adapter *adapter)

spin_lock_init(&adapter->ptp_tx_lock);
spin_lock_init(&adapter->tmreg_lock);
- INIT_WORK(&adapter->ptp_tx_work, igc_ptp_tx_work);

adapter->tstamp_config.rx_filter = HWTSTAMP_FILTER_NONE;
adapter->tstamp_config.tx_type = HWTSTAMP_TX_OFF;
--
2.39.2